Hitherto, optical filters attached to lenses of cameras to restrict light entering the lenses have been used. Optical filters are generally used for the purpose of restricting a wavelength range of transmission light. In addition to such a purpose, some optical filters are used as means for giving effects (hereinafter referred to as special effects) that allow a subject to be modified with increasing distance from a reference point set on a screen. Such special effects include an effect (hereinafter referred to as a zooming modification effect) that allows a subject to be modified so as to look as if the subject is radially flowing with increasing distance from the reference point, and an effect (hereinafter referred to as a cyclone modification effect) that allows a subject to be modified so as to look as if the subject is spirally flowing with increasing distance from the reference point. Since optical filters for giving such special effects (hereinafter referred to as special-effect optical filters) are generally designed so that the reference point described above is placed at a center point on the screen, a desired point on the screen cannot be used as a reference point to give the special effects as described above. In addition, special-effect optical filters need to be attached to lenses of cameras only when special effects are to be given. Moreover, images captured when special-effect optical filters are attached to lenses of cameras suffer resolution degradation over entire screens thereof.
Furthermore, in computers, by executing image processing software, similar special effects can be given to captured image data of even images captured when the special-effect optical filters described above are not attached to lenses of cameras. Such image processing software can give a special effect to a processing-target image by setting a desired position on a screen as a reference point. Specifically, such image processing software converts image data into a plurality of images enlarged at different enlargement ratios with respect to a reference point. And, the image processing software superimposes the plurality of enlarged images on unprocessed image data to give a zooming modification effect to the original image.
Due to the improvement in processing capability of computation processing processors provided in digital cameras, image processing for giving a special effect that allows a subject to be modified with respect to a reference point, including a zooming modification effect, is performed not only in personal computers but also in digital cameras. That is, digital cameras have comparatively facilitated, due to the improvement in processing capability of computation processing processors thereof, not only the process of simply recording and displaying captured images but also the process of giving special effects to captured images. Meanwhile, in digital cameras, with the increase in the number of pixels of a captured image in order to meet a demand for high image quality, the amount of computation necessary to give an image effect to image data has also increased. Thus, due to the lower processing capability than personal computers, digital cameras have a problem in that the computation speed is also comparatively reduced with the increase in the amount of computation described above. In addition, digital cameras are mainly driven by battery power sources, and power consumption also increases with such an increase in the amount of computation, resulting in another problem in that the driving time is shortened.
In an image processing method described in Japanese Examined Patent Application Publication No. 7-113961, a high-brightness portion on a screen is detected and shifted in a predetermined direction with a signal corresponding to that portion being applied with a predetermined weight and is added with a brightness signal component to thereby give a cross filter effect, which is used as a special-effect optical filter, to an image. Using such image processing as described in Japanese Examined Patent Application Publication No. 7-113961, a plurality of pixel values of individual pixels are shifted and added so as to be increased with respect to a reference point, whereby a pseudo-zooming modification effect can be given to a captured image. In a case where a zooming modification effect is given to a captured image using such an image processing method, however, the amount of processing involved in the process of extracting a high-brightness point or the addition process, described above, increases in accordance with the number of pixels of the captured image. In such an image processing method, further, a pixel that is not extracted as a high-brightness pixel is not to be processed. In such an image processing method, therefore, no zooming modification effect can be given to a region composed of unextracted pixels.